District of Columbia Mayor Vincent Gray said Wednesday that he still believes he's the best person to lead the city despite revelations that he was elected with the help of a $650,000 in illicit funds, and he said he has no plans to resign.

Three members of the D.C. Council, however, said Gray's 2010 victory was irreparably tainted and called on him to step down for the good of the district. One, a former ally, said Gray was responsible for "massive election fraud."

Speaking carefully and cordially to reporters at a news conference in an alley in Northeast Washington, Gray sought to draw a distinction between the illegal activity that occurred during his campaign and the way his administration has performed since he took office.

On Tuesday, a Gray campaign aide pleaded guilty to conspiring with a district businessman to spend $650,000 in illicit funds on campaign materials, consultants, canvassers and other expenses. The money aided Gray's Democratic primary victory over then-mayor Adrian Fenty and was not noted on campaign finance reports. U.S. Attorney Ronald Machen said Gray's victory was tainted by the effort because voters had no way of knowing how the campaign was funded.

"This is not the campaign that we intended to run," Gray said. "I got into this for the right reasons."

Asked whether he would finish his term, Gray said: "I have no plans to do otherwise."

Gray said he still thought he was the best person to lead the district, and he pointed to the progress the city has made on public safety, financial stability and environmental protection since he took office.

But councilmembers David Catania, an at-large independent, Mary Cheh, a Ward 3 Democrat, and Muriel Bowser, a Ward 4 Democrat, said Gray should take responsibility for the campaign misdeeds and resign.

"Whether or not he knew of the massive election fraud that was taking place in his name, he was responsible for it," Cheh said in a statement. "I believe that he would do a great public service if he would step aside now."

Cheh endorsed Gray in 2010, a politically risky move because her affluent ward favored Fenty by a wide margin. She said she was saddened by her call for his resignation because she had believed in his integrity.

Catania, a frequent critic of Gray, said: "Whether the mayor knew of the shadow campaign or not does not matter. He should not be the beneficiary of that illegality."

If Gray were to step down, Council Chairman Phil Mendelson would replace him on an interim basis. Mendelson became council chairman just last month after former chairman Kwame Brown pleaded guilty to bank fraud and resigned. Mendelson said in a statement that calls for the mayor's resignation were premature because Gray himself has not been accused of a crime.

Also this year, former councilmember Harry Thomas Jr. stepped down after admitting he embezzled more than $350,000 in city funds. He is serving a 3-year prison term.

Gray has said little about the investigation in recent months, and he said Wednesday that he was unable to discuss it in the detail that he would like because the probe is ongoing. He acknowledged, however, that he was deeply concerned about the activity that his campaign operatives have revealed in federal court.

In addition to Eugenia "Jeanne" Clarke Harris, the public-relations executive who pleaded guilty Tuesday, two other campaign aides have pleaded guilty to funneling money to a minor mayoral candidate and conspiring to cover up the payments. The candidate, Sulaimon Brown, was paid to stay in the race and continue making negative comments about Fenty, the aides said. Brown was later hired by the Gray administration, although he was fired after less than a month. Gray has said he was unaware of the payments and did not promise Brown a job.

Asked if he was corrupt, Gray said: "There are lots of people who probably will have that question. I know who I am. I get up in the morning every day and look in the mirror and I see somebody I respect."

Although the name of Harris' co-conspirator was not revealed in court, two people familiar with the investigation have told The Associated Press that the businessman accused of funding the shadow campaign is Jeffrey Thompson, a partner in an accounting firm who also owns a managed-care provider that is the city's largest contractor. The individuals spoke on condition of anonymity because they were not authorized to disclose the information.

Gray did not directly answer a question about whether Thompson handed him checks, but he said no candidate could be expected to personally vet every contribution.

Harris also pleaded guilty to conspiring to make straw contributions and said her co-conspirator would "bundle" the checks and hand them directly to candidates he supported. The co-conspirator later reimbursed the straw donors, including Harris, according to her plea.